METHOD STATEMENT UNDER GROUND PLUMBING WORK

1. Objective

This method statement provides information concerning the method of construction to ensure compliance with contract requirements, drawing, technical specification and quality control to provide a successful installation, testing, and commissioning of the Installation of U/G UPVC Pipes.

• Scope

HAC shall complete installation of uPVC pipes including excavation and backfilling, testing, witness testing at the site by the engineer, testing and commissioning of the underground drainage work.

• References

• Contract Specifications.
• Material Submittal.
• Technical Literature for Manufacturer.
• Design Drawings.
• Shop Drawings.

• Material

• Pipes are uPVC pipes PN10 as per approved one.
• Fittings are EEPCO/APLACO UPVC Fittings
• Joints are Rubber Joints

• Material Procurement, Handling and Storage

• Upon approval of the material and shop drawing submittals, Contractor shall survey the QTY including fittings as per approved shop drawing and purchase the material as per project schedule.
•   Upon delivery to site, all pipes and fittings shall be stored indoor, in a clean, dry and ventilated place (as per attached recommendation).

• Trenching & Bedding
• Prior to start of excavation, make sure that the pipe line coordinates and elevation has been checked and verified by the surveyor.
• Excavation and sand bedding shall be done mainly by equipments (excavators and loaders).
• Manual excavation is required in cases where equipments are not possible or are not allowed due to safety reasons or where manual excavation is more convenient in a specific area.
• Excavated materials shall be placed at a suitable distance from the edge of excavation so that materials do not fall back into the trench or excavated materials will be put directly to a dump truck and will be unloaded to a designated area away from the trench.
• Loaders shall be used for placing sand bedding materials into the trench while labors will spread manually to meet the correct elevation and slope throughout the trench.
• The minimum trench width from the bottom to 300 mm above the top of the pipe shall be 300 mm for pipe size 90 mm & below and 300 mm + Outside Diameter for pipe size 100 mm & above.
• Depth of trench shall be dug deep enough to provide a ground bed of at least 150 mm from the bottom of the pipe.
• Clean sand bedding layer of 150 mm thickness shall be compacted to at least 95% Proctor density.
• The trench bottom shall be continuous, smooth, and free of rocks and to the line and grade shown on the approved installation drawings.

• Backfilling

• Make sure that Inspection & Testing has been done and approved before any backfilling works starts.
• Protect top 30 cm of the pipe by backfilling using sand.
• Backfill the remain trench by backfilling material (25 cm max. thickness)
• Backfilling shall be done mainly by equipments (loaders & compactors) while some labors spreading manually the sand and backfill materials wherever required.

• Assembly, Joining & Laying
• Before assembly, each pipes and fittings shall be examined from damages.
• Make certain pipe ends and gasket areas are free of dirt and debris. Support spigot end of pipe above ground to prevent dirt contamination when lubricant is applied.
• Apply a light coating of recommended lubricant to spigot end and sealing section of gasket.
• Align pipe ends. Push spigot end into gasket bell so that the reference mark is even with the entrance of the gasket bell.
• If pieces of pipe are used, make a precise, perpendicular cut. Then, bevel using suitable equipment, to avoid damaging the gasket during connection.
• Before start of the pipe laying, the bottom of the trench shall be dry, continuous, smooth, free of rocks and to the line and grade shown on the installation drawings.
• For buried pipes supports
• Pipe location, elevation and slope shall be maintained by a surveyor. A survey report shall be made after final installation.
• Sand bags shall be placed at the bottom of pipes for underground drainage work (and supports for buried pipes) to meet the exact elevation and slope of the pipe being installed. The sand bed shall be then adjusted accordingly to maintain the pipe on the ground is on a firm bed for its entire length.
• Excavation a little deeper on the place where the pipe is to be joined shall be done to allow access for the installer for proper joining method.
• Pipe shall be installed continuously downhill without low points and high points.
• Pipe is to be anchored by partial sand covering of the pipe to prevent floatation and to maintain its alignment and level.
• At the end of every work shift, personnel performing the pipe installation shall ensure that the pipe ends are capped to prevent entry of foreign materials.
• Reservation in the manhole base shall be done in order to allow connections to manhole after manhole pouring.
• Grouting shall be applied between manhole and outside diameter of pipe.
• In case of drain outlets connections (at the landscape area), no external connection is allowed (e.g. No-hub coupling) only push on connection is allowed.

• Gravity Test
• Gravity test shall be done from manhole to manhole or a column of water equivalent to the rim elevation of the upstream manhole if pipe is to be tested separately.
• Gravity test shall be maintained for a period of 4 hours for lines whose joints have not been backfilled or are above ground piping while 24 hours shall be maintained for lines whose joints have been backfilled.
• An extension pipe is provided on the test plugs at selected location for water filling and drain points and at least one pipe riser for the water head required that shall be accessible for visual inspection.
• Water filling into the pipe being tested shall be from a water truck or a ground level water tank with electric or engine-driven pump. A water hose shall be placed direct to the manhole, to the pipe being tested or to a pipe connection.
• All joints shall be exposed and cleaned for visual inspection.
• Partial sand covering and backfilling on the body of the pipe being tested shall be done to prevent floatation during test.
• Leak test for the installed pipes is to be carried-out with presence of inspector Engineer.
• Cap end or plug as required and fill with water to produce 3 meters head (if applicable) at highest point of section tested. Let stand with no loss of level for a period of four hours.
• After the approval of Inspector Engineer, cover the pipes with cement plaster or sand to where it is applicable.
• No special device or equipment to be used for the gravity test of underground piping.
• By simply marking the water level at the manhole or pipe being tested at the start of the test, the piping being tested shall be considered satisfactory if no reasonable drop on the water level after the specified test period and if no evidence of water leakage on the body of the pipes, fittings and to the joints.
• During Inspection, all exposed pipes, joints and fittings shall be carefully examined for leakage.
• The piping being tested shall be satisfactory if there is no evidence of leakage or reasonable drop in the water head after the specified test period.
• Leaking pipes, joints and fittings shall be replaced and test shall be repeated until the system is proven satisfactory.